I know how to use my MIDI keyboard in GarageBand for instance and play it with different instruments etc. But what I want is to be able to play a few notes here and there even when I'm in the middle of doing something completely different. I.E. I want my keyboard to be identical to a normal piano/synth that's always available for me to play music.

Leave GarageBand running in the background at all times?
– slimJan 9 '14 at 14:07

@slim GarageBand and other DAWs use significant CPU, memory, and hard drive resources, so it's preferable to use something lighter weight if possible.
– KevinJan 10 '14 at 4:48

I do just that pretty frequently. There is a tradeoff between performance and sample quality (SimpleSynth could do the same thing with a fraction of the resources), but when you're running 16 gigs of RAM it's less of an issue.
– NReilinghJan 14 '16 at 15:19

9 Answers
9

If you want your Mac to be part of the system, you'll need to leave your Mac on running the software that is producing the sounds at all times, but that doesn't seem to match a "simple always-on piano".

Samplers need a lot of resources, and having one on your system 100% of the time might be impractical.

If you still want to use your Mac, I recommend you to don't leave the sampler software running all time. Just run it when you need it. There are many lightweight AU hosts that you can use to run your samplers, synths, and other instruments. Some options are:

I've written on this site before about Pianoteq Stage, a US$129 / €100 app that has very low CPU, RAM and hard drive space requirements and makes a wonderfully realistic and expressive acoustic piano sound. It is available for Windows, Mac and Linux.

It comes as a small-footprint stand-alone app, as well as a VST and Audio Unit plugin. You could run the stand-alone app in the background all the time without needing to have a resource-intensive DAW or VST host running.

Pianoteq Stage is available in a free limited demo version; download it and give it a try.

AU Lab allows you to connect MIDI channels to sound modules called "Audio Units". Audio Units are the standard for instrument and effect plugins in the OSX world.

So you will also need a piano audio unit. It's possible that you'll find the standard GarageBand piano is an audio unit which you can access from AU Lab, but if not you'll need to find a piano audio unit you like. A Google search for "audio unit piano" reveals several, ranging from free to very expensive.

Of course, you're not limited to piano sounds, and some there will be AUs that are less memory and CPU intensive than a realistic piano simulation.

Note that any AUs you install can also be used from GarageBand, Logic and most other DAWs.

4Front Piano is the first free piano AU I found on KVR. I have not tried it myself, so this is not a recommendation. It claims to be "small on memory and CPU usage".

However this is a reasonable amount of trouble to go to, when it seems to me that simply leaving GarageBand running would do the job. Leave it open on a song with only one track, a piano track.

GarageBand takes a while to load, but if it's not recording, playing back, or monitoring a real instrument, then its CPU load should be minimal, and it should not be doing disk IO. Although its memory footprint is large, most of it will be swapped out to disk, leaving only the blocks necessary to handle piano playing in RAM. Indeed, if you work your Mac hard with other memory-intensive tasks, then try playing piano, you'll notice a delay while it brings those blocks back from swap.

Even if the app is lightweight itself, the AU samplers it will run tend to furiously eat resources. It will slow down his system considerably. That's an important thing to take into consideration: the app is one thing, but the AUs will ask for their own piece of the pie.
– Von HuffmanJan 10 '14 at 14:14

@JCPedroza "Furiously"? Surely that depends on the AU. The options run the full gamut from a simple FM Synth (should be very resource-light) to something with multiple high-bitrate samples for each note (will chew up memory).
– slimJan 10 '14 at 14:33

@Slim I referred to AU samplers specifically, not synths. Since the question was regarding both piano and synth sounds, I assumed that he'll need both samplers and synths. Samplers are inherently resource hungry, a lot of his RAM will be eaten 100% of the time.
– Von HuffmanJan 10 '14 at 14:37

@JCPedroza OK, yes, if you want to make memory-intensive noises, you can't avoid using memory. Although as discussed, if you stop playing, and the system needs the RAM, the OS is likely to swap those blocks to disk.
– slimJan 10 '14 at 14:42

Well its not instant but I use software on windows called cantabile. Its ment for live performance where you make instrument arrangements. I have a couple of projects with various virtual instruments configured and shortcuts on my desktop. If I want to practice I double click the project, power on the keyboard and then can play in a few second. I have everything on a ssd so that helps dramatically in loading time.

I am really satisfied with this solution and guess that a similar setup must be available on mac.

This is actually pretty easy to do if your keyboard has its own sounds.

Connect your keyboard to a small mixer, a $100 Tapco will do. Then have your external speakers connected to the mixer. Have your Mac run a line into the mixer.

This turns your Mac sounds into a simple line in, and you can raise or lower levels on the mixer. Just a little 4 channel one is all you need. Also, your volume knob on your keyboard will turn your piano, or whatever sound you are running from your keyboard up down or obviously, off if you want it or are working in Logic, garage band, whichever.

Another option if you happen to already use Google Chrome is just using a "web audio" synth of some kind. These are virtual instruments written in JS that run in a web browser. There are a lot of demos around and some of them support using a MIDI controller. For instance here's one that emulates a DX7:

You won't get the greatest performance or latency, so it's really not for serious work. But if it's just to "play a few notes here and there", it may be just what you need given that you can just keep a browser tab open or click a bookmark to get to it.

The one caveat, besides the performance, is that only Google Chrome and other browsers based on the Blink browser engine support web MIDI so far.

So I just downloaded a critter called GM Player from the iTunes App store, on a whim. Based on previous posts, I was about to give it up and just use Garageband. But GMP is doing exactly what I wanted: simple interface that allows me to pick out my harmony parts in vocal performance music using my little Akai MPK mini. When not in use it is currently holding at around 15-18% CPU usage, according to Activity Monitor. This is fairly space-hungry for something not actively contributing to life--but I won't leave it on all the time. It's up and running very quickly, so no big deal. Oh, and it stays available even when the screen times out--When it's on, it's on.

Before you discount simply leaving Garage Band running, try. Yes, it can use a lot of resources. But today's computers HAVE a lot of resources - a ridiculous amount, if the other tasks are things like writing a document or doing email - and you're only asking GB to manipulate the samples for one instrument.

Sounds like swapping your keyboard for one with onboard sounds might be a good buy for you though. It doesn't have to be expensive.

Yeah, I leave Logic running almost all the time for precisely this use-case. I mean I use Logic for normal recording purposes, but I also leave it open throughout the day on an electric piano preset just so I quickly sit down at the keyboard and play for a few minutes here and there. I don't have a new or particularly powerful iMac and it works just fine even while doing other things.
– user37496Apr 14 '17 at 22:27

I used to use AU Lab for this purpose, but it slowed down the system considerably. Then I discovered Hosting AU and never looked back. I can’t even measure how little CPU it takes and it allows me to save configuration profiles (unlike AU Lab). After (down)loading few instruments’ sound banks I’ve never been happier with my MIDI keyboard setup.